This is overall a really fun little tower defense game. I like the games music and most of the visuals is pretty good, but especially the background tiles looks a bit blurry. The game could use a bit more speed options, and it's a bit difficult too see where bugs comes from and where they goes toward. The tutorial and upgrade system overall works very well, but it's a bit weird that the defense bugs works a bit different then the same kind of attaching bugs.
But overall is this a fun and pretty well made tower defense game. Well done.